Thermostat



Oct. 7, 1952 c. E. ARMSTRONG 2,613,293

THERMOSTAT Filed Sept. 12, 1949 CHARLES E. ARMSTE o/vG,

INVENTOR.

Patented Oct. 7 1952 UNITED STATES PATENT OFFICE THERMOSTAT Charles E.Armstrong, Portland, Oreg.

Application September 12, 1949, Serial No. 115,168

1 Claim. 1

This invention relates to improvements in temperature sensitiveswitching mechanisms and more particularly to a switch of this characterembodying a Micro switch and a temperature sensitive element in the formof a bi-metallic strip for actuating said switch. One of thecharacteristics of a Micro switch is that the amount of travel requiredto actuate or depress its plunger is extremely small while the requiredpressure of force is relatively high.

Accordingly, it is one of the principal objects of my invention toprovide a switch of this character wherein the thermostatic element isrequired to move only a short distance to apply, through leverage, therelatively high pressure necessary to actuate the plunger.

A further object is the provision of a switching mechanism which is ofsimple, efiicient, durable and inexpensive construction, compact in sizeand operable within close temperature differential.

These and other objects will appear as my invention is more fullyhereinafter described in the following specification, illustrated in theaccompanying drawing and finally pointed out in the appended claim.

In the drawing:

Figure 1 is a top plan view of the invention.

Figure 2 is a side elevation of Figure 1.

Referring now more particularly to the drawing:

Reference numeral I indicates a base made of any approved type ofinsulating material and flanged as at 2 to accommodate any approved typeof housing upon which may be mounted the usual mercury thermometer.Rotatably mounted upon the base by means of a screw 3 is a knurled wheelor disk 4 inscribed with numerals representing various degrees oftemperature. Secured to the disk or formed integral therewith is a cam5.

At the opposite end of the base I mount a Micro switch 6 by means ofscrews 1 and 8. Wires 9 and In of an electrical circuit are connectedwith the switch and a circuit through the wires is opened or closed by aplunger II which operates the switching mechanism.

Rotatably attached to the base by means of a screw I2 is a collar 13 towhich is secured one end of a temperature sensitive element in the formof a strip of bi-metallic material 14. The end of the bi-metallic stripis partially coiled about the collar I3 and is secured thereto by anysuitable means, such as soldering or the like. The opposite end of thebi-metallic strip is offset as shown and is provided with an adjustingscrew 15 always in contact with the operating surface of the cam 5. Thestrip 14 is offset only for the purpose of rendering It will be notedthat the distance between the the assembly more compact.

screw l5 and the switch plunger 1 I is many times greater than thedistance between the plunger and the screw l2 about which thecorresponding end of the bi-metallic strip pivots. The amount ofleverage established by this arrangement applies ample downward pressureto the plunger by the mere deformation of the bi-metallic strip in itsmovement from the full line to dotted line position, shown in Figure 1,under the influence of a rising temperature. The normal spaced relationbetween the bi-metallic strip and the plunger 1 I may be minutelyadjusted by the screw 15 against the cam 5. The plunger is provided witha spring-return mechanism to urge it upwardly at all times into contactwith the thermostatic element or in adjusted relationship thereto asaforesaid.

While I have shown a particular form of embodiment of my invention, I amaware that many minor changes therein will readily suggest themselves toothers skilled in the art without departing from the spirit and scope ofthe invention. Having thus described my invention, what I claim as newand desire to protect by Letters Patent is:

A thermostatically actuated switching mechanism comprising incombination, an elongated base, a single length of bimetaltemperaturesensitive controlling element extending substantially fulllength of the base and pivotally attached at one of its ends to one endof the base, a cam rotatably mounted on the opposite end of the base,the opposite end of said bimetal element being in adjustable contactwith the cam, a switch mounted on the base near said one end thereof, aspring-urged plunger extending outwardly from the switch for actuatingthe switching mechanism, said plunger being in contact with said bimetalelement and positioned at a point closer to said pivotal attachment ofthe bimetal element than to the center of said bimetal element wherebysaid plunger will be depressed with maximum pressure upon minimumtemperature rise and released with minimum temperature fall.

CHARLES E. ARMSTRONG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,756,660 Perry Apr. 29, 19302,111,816 Shaw Mar. 22, 1938 2,171,273 Cunningham Aug. 29, 19392,249,259 Shaw July 15, 1941 2,289,973 Lake July 14, 1942 2,336,408Matthews Dec. '7, 1943

